The objective of our research project is to obtain methods to confidently identify each and every cell type of the mammary gland (epithelial, fibroblastic, adipose, and myoepithelial) that can be used on isolated cells in cultures. Our approach is to develop antisera that identify cell-type specific antigens (differentiation antigens) on the cell surface. We have already shown that epithelial cell-type specific antigens are expressed in both normal and neoplastic breast epithelial cells from both the human and mouse. We are purifying and characterizing these specific antigens and preparing purified specific antisera. Using these specific antibodies, methods will be developed to quantitate the antigens on individual cells, and to identify and separate different cell types of the mammary gland. In addition, we will study the expression of differentiation antigens with regard to its genetic and developmental implication in normal and neoplastic cells.